1. Field of the Invention
This is an improvement of a previous application filed by the inventor on Feb. 9. 1977, entitled Universal Drafting Triangle with Ser. No. 766,877 now U.S. Pat. No. 4,121,344. The present invention refers in general to drafting tools and in particular to a new and useful digital measuring device for visually displaying the displacement of a vertical straight edge and a horizontal straight edge of the device over a drafting surface.
2. Description of the Prior Art
In the inventor's previous application for a UNIVERSAL DRAFTING TRIANGLE, which is incorporated by reference in this application, there is described a drafting aid which replaces the functioning of a T-square and triangle arrangement on the conventional drafting table with a single integrated unit which comprises a first right triangle member which can be placed upon and be slid along a conventional T-square or parallel straight edge which is provided on most modern drafting tables. This first triangle provides a vertical straight edge which can be utilized in a conventional manner to draw vertical parallel lines on a drafting surface. A second triangular member is engaged with the first triangle and slidable along its vertical edge. A drive means which comprises a hand operable wheel is mounted in the first triangle and connected to the second triangular member so that a draftsman may manipulate the drive wheel by rotating it in one direction or the other, thereby raising or lowering the second triangular member with respect to the first triangle. The top edge of the second triangular member is provided in parallel orientation to the T-square or parallel straight edge on the drafting table and through the manipulation of the drive wheel, a draftsman using one hand can raise or lower the striaght edge of the second triangular member and draw a series of parallel horizontal lines. The entire system, therefore, enables a draftsman to draw horizontal as well as vertical parallels using one hand to engage, hold and manipulate the device, and thereby leave the other hand to do the actual drawing. The Universal Drafting Triangle therefore provides a single drafting tool that reduces the amount of manipulation requried in aliging various drafting tools which were previously required to draw any number of lines on a drafting surface.
As with any conventional drafting tool the Universal Drafting Triangle can be provided with scaled markings to indicate distances on both its horizontal and vertical straight edges. By reading off markings a draftsman can, in a conventional manner, mark off, for example, equally spaced vertical or horizontal lines. Such a conventional method of marking positions on a drafting surface results in eye strain as well as opens the door to incorrect interpretations of markings and graduations on the scale which are unavoidable after long hours of drafting. Further complications arise when the scale on a drawing must be changed or where a drawing must be made from other drawings of a different scale. At the present time draftsman are also faced with the conversion of changing drawings scales from the English measuring system to the metric system. Although such a conversion requires a simple multiplication of one unit of measure by the other, such a conversion results in the numerical values of distances and scales being entirely different in one system from that in another. A draftsman, therefore, loses any simple relationship he might be able to utilize in converting a drawing from one system to the other. For example, a drawing which must be reduced in scale from one inch equals one foot to 1/4 inch equals one foot can simply visualize the conversion by quartering any measurement he takes from the drawing to be copied. When converting from English to metric, however, the draftsman must multiply his English measurements by a fractional number which at best is approximate and which is difficult if not impossible to visualize quickly.